In a multi-type air conditioner in which a single outdoor unit and a plurality of indoor units are connected, a refrigerant circuit is formed between an outdoor heat exchanger disposed in the outdoor unit and an indoor heat exchanger disposed in the plurality of indoor units. In this case, branching pipes must be provided to the refrigerant pipe disposed between the outdoor heat exchanger and the indoor heat exchanger in order to transport refrigerant to each of the plurality of indoor heat exchangers.
The branching portion provided to such branching pipes may be provided with a thermistor for detecting the refrigerant temperature, a motor-operated value for adjusting the refrigerant pressure, a vapor-liquid heat exchanger for heat exchange between refrigerants, and electrical parts and other components for controlling the motor-operated value on the basis of the refrigerant temperature detected by the thermistor. The branching portion provided with such branching pipes, thermistor, motor-operated valve, vapor-liquid heat exchanger, and electrical parts and other components is generally accommodated in a casing to constitute a refrigerant relay branching unit.
The branching pipes in the refrigerant relay branching unit have areas in which the temperature is lower than the surrounding temperature because the refrigerant flows into the low pressure pipes, and condensation is liable to form in such a low temperature area.
In contrast, a unit having an insulated structure has been proposed in which the interior of the casing is filled with urethane or another insulation material, as shown in Patent Document 1 described below, in order to prevent such condensation from being generated. In this structure, the insulation material is filled so as to completely encompass the branching pipes, and condensation is avoided by preventing air from coming into contact with the low temperature areas of the branching pipes.
<Patent Document 1> Japanese Laid-open Patent Application No. 10-238900